An example of a gas turbine engine of the type to which the present invention applies is a gas turbine engine having a compression section, a combustion section and a turbine section. An annular flow path for working medium gases extends axially through such an engine. A rotor assembly extends axially through the compression and turbine sections and is circumscribed by a stator assembly. The stator assembly includes an engine case. Rows of rotor blades extend outwardly from the rotor across the working medium flow path in both the turbine and compression sections. An array of stator vanes extends inwardly from the engine case across the working medium flow path at the downstream end of most blade rows for directing the working medium gases of the engine into the next working station of the engine.
Examples of engine structures employing rotor blades and stator vanes inwardly of an outer case are shown in: U.S. Pat. No. 3,966,354 issued to Patterson entitled "THERMAL ACTUATED VALVE FOR CLEARANCE CONTROL"; U.S. Pat. No. 3,992,126 issued to Brown et al. entitled "TURBINE COOLING"; and U.S. Pat. No. 4,011,718 issued to Asplund entitled "GAS TURBINE CONSTRUCTION".
As shown in these patents, the combustion section of the engine is used to burn fuel in the engine to add energy to the working medium gases. As the hot, working medium gases are expanded through the turbine section of the engine, the arrays of rotor blades and stator vanes immediately downstream of the combustion section are bathed in the working medium gases. In this region of the engine, cooling air is flowed inwardly of the outer case to the interior of the stator vanes to maintain the temperature of the stator vanes within acceptable levels.
At some location downstream of the cooled arrays of stator vanes cooling air is not flowed to the interior of the vanes. An example of such a construction is shown in U.S. Pat. No. 3,644,057 issued to Steinbarger entitled "LOCKING DEVICE". Even though the stator vanes are not cooled internally, efforts are being made to ensure that the stator vanes and associated components are not unacceptably heated by the hot working medium gases. Accordingly, scientists and engineers are working to develop a stator assembly employing stator vanes which avoids the unacceptable heating of the stator vanes and components associated with the stator vanes.